The objective of this research is to determine in human subjects the safety and efficacy of the titanium blade implant. Patients between ages 21 and 55 exhibiting unilateral and bilateral edentulous mandibular sites posterior to the first bicuspid will be treated with 120 four-unit fixed partial dentures, double abutted anteriorly to the cuspid and first bicuspid. Blade Implants will be placed to act as the distal abutments for 60 of these restorations which will be compared to the other 60, remaining as distally unsupported cantilever fixed partial dentures. Treatment will be randomized and patients stratified by opposing dentition - fixed or movable, and site -unilateral or bilateral. Implant insertion and patient treatment will be performed over a 4-year period. Post-treatment follow-up is projected for 5-year survival. This trial will be supplemented by planned multicentric trials if 3-year results warrant expansion of the study.